The wheel bolt hole assembly part involves in the safety of automobile assembly, and when a powder spraying process is performed on a wheel, the protection on the mounting part of a bolt hole is extremely important. Shielded protection adopted in the wheel surface powder spraying technical field at present has the following defects: protective plugs need to be assembled and disassembled artificially, so that the labor intensity and the cost are high; a lot of different types of protective plugs needed for wheels having a variety of bolt holes are inconvenient to customize and store and high in cost; the protective plugs assembled and disassembled artificially are easy to miss or misplace, thus causing rejects; the paint drop treatment needed after the protective plugs are used for a period of time may pollute the environment, and a large batch of rejects may be caused by incomplete cleaning; and the protective plugs may drop when equipment vibrates, thus causing rejects, chain blockage and equipment fault.